Engineers transform smartphone into blood pressure monitor, thanks to a 10-cent plastic clip

UC San Diego engineers developed the low-cost clip that enables easy and affordable monitoring in resource-poor communities.
Kavita Verma
Prototype of the blood pressure monitoring clip.
Prototype of the blood pressure monitoring clip. The user presses on the clip and a custom smartphone app guides the user on how hard and long to press during the measurement.

Digital Health Lab / UC San Diego 

University of California San Diego engineers have created a low-cost clip that makes use of the camera and flash on a smartphone to measure blood pressure at the user's fingertip.

This innovative clip, which can be produced at scale for as little as 10 cents, has the potential to revolutionize routine blood pressure monitoring and make it available to people in resource-poor regions. 

The research was published in Scientific Reports on May 29.

Enhancing accessibility and affordability

The low-cost, straightforward clip that UC San Diego engineers created revolutionizes blood pressure monitoring, especially for people with limited access to healthcare. The team, led by Yinan (Tom) Xuan, seeks to lower obstacles to monitoring, a press release stated. 

Its calibration-free operation, in contrast to other systems that require cuff measurements, is a noteworthy advantage. Director of the Digital Health Lab Edward Wang emphasizes that the clip offers reliable readings without the need for extra apparatus. 

This feature makes measurement easier, improving accessibility and convenience. The tech has a big potential because it provides a cheap and simple way to treat illnesses like hypertension.

The clip's operation and validation

The user applies pressure with a fingertip while following instructions from the unique smartphone app to measure blood pressure using the clip. The clip, a plastic attachment that was 3D-printed, covers the smartphone's camera and flash. 

Its optical structure is similar to a pinhole camera. When pressure is applied, the fingertip is illuminated by the flash, and the generated light is transmitted to the camera through a pinhole-sized channel, creating a picture of a red circle. 

The diameter and brightness of the circle reveal details about the pressure being applied and, separately, the amount of blood in the fingertip. Following the algorithmic processing of these measures, systolic and diastolic blood pressure readings are obtained.

Twenty-four volunteers from the UC San Diego Medical Centre participated in validation tests to show that the clip's outcomes were comparable to those obtained using a blood pressure cuff. This novel approach's accuracy and affordability make it a viable tool for self-monitoring blood pressure, especially in older persons. 

The researchers believe that the current design of the clip should work with different phone types even though it has only been tested on one specific smartphone model.

The team's future goals include improving the technology's usability for older persons in particular and validating its accuracy for a range of skin tones. They also aim to create a more ubiquitous design. 

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